Tuning indicator system



Nov. 21, 1950 H. T. J. WIEGERINCK ETAL 2,530,847

TUNING INDICATOR SYSTEM Filed Feb. l2, 1947 Patented Nov. 21, 1950 UNITED STATES TUNING INDICATOR SYSTEM Hendrikus Theodorus Jozef Wiegerinck and Johan Hendrik van Wageningen, Eindhoven, Netherlands, assignors to Hartford National Bank and Trust Company, Hartford, Conn., as

trustee Application February 12, 1947, Serial No. 728,060 In the Netherlands July 15, 1944 `Section 1, Public Law 690, August 8, 1946 Patent expires July 15, 1964 Thisinvention lrelates to a circuit-arrangement `for the indication 'of the frequency of electric loscillations, 'andf'fmore particularly 'for `ind1cat- `.ling :the correct tuningrof a tunable receiver, such as a'r'adio or television receiver,Y with the use of a vfrequency detector. Itfhas'been suggested vto secure an `indication fof' the correct tuning of a'radio receiver by ccmp'aring two voltages robtainedtroma network lwherein `one of the vvoltages is higher Lor 4lower vrespectively than 'the fother voltage, depending -upon Whether the frequency of the intermediate frequency oscillations supplied to the .network is higher `or lower than the desired lintermediate "frequency Atthefcorrect tuning, the two voltageslare equal. :In-thiscase, the'two voltages to be compared are each taken from a-resonant circuit; theresonant lcircuits being coupled "to the "intermediate "frequency ampliiier and being `tuned respectively -to frequencies that are higher V'or .lower than theY desired intermediatefrequency and whichdiier from the intermediate frequency by the same amount.

' According to the `present invention, the `frein a positive ora negative sensedepending upon whether the frequency-of the oscillations'diverges `in one orfin theoth-er Adirection from the frequency to which the circuit istuned. This voltage Vor a voltage obtained therefrom is' supplied'to` at least two 'input electrodes of adischargesystem whichf-in'add-ition, comprises a cathode and two or more further electrodesfand; also by suitable adjustment of `the discharge system, yiniiuences the current distribution between the electrodes in'fsuch--manner that a voltage suitable forthe indication :is obtainable froml at least oneof these electrodes. This voltage exhibitsian 'extreme value V when the frequency of the 'electric oscilla-tions corresponds with `fthe frequency jto which the circuit is tuned.

The-discharge system -is preferably constituted The indication voltage example 1a cathodeerayfindicator system.

`Inr orderthat the t .invention may I be clearly `understood and readilyca'rried into' eiiect, it will -now be set outmore--iully with reference -to the --accompanying drawing, in :which Figs. l through dillustrate embodiments of- 'fthe invention.

VVFig. almshows a circuitearrangement for-findicating the correct tuning -of a wireless receiver :designed e .for ithe reception of -ff-requency-modu lated signals. The receiver comprises kadire- "quencydetector 'supplies avotage Whichvvaries i vquency detector .41, from which is derived avolt- :"age lwhich varies in a positive or a negative sense dependingupon whether the frequency towhi'ch the receiver is tuned differs in one or in the other direction from the carrier wave frequency of the 'incoming signal. This voltage is supplied to terminals designated I and then conductedto the control-grid 2i of a pentode 2. The anode 24 :of this pentodeis connected via a resistance 3 andthescreen grid 22 via a potentiometer 4 to the 'positive terminal of a direct current source (not shown). `In addition, the pentode 2 is provided 4with -negative vfeedback by means of a `resistance 5 included in the cathode lead. The suppressor grid 23 is connected to that end --of 'the lresistance 5 which is remote from the cathode :2(i; :so that 'the voltage across .the resistance i5 (this voltage being consequently obtained from the voltage comi-ng 'from the frequency detector `IH) is also imparted to the suppressor grid 23.

`The indication voltage is obtained from the anode fof the tube 2. For this purpose the anode 24 is :connected to earth via a potentiometer 6 and a .source of direct voltage l. The indication voltage is taken from the potentiometer 6 and supplied Cto .a .cathode-ray indicator system. This indicator 'system comprises two triodes and the cathiode-ray indicator proper which are jointly housed :in a single tube 8. This system is otherwise wellknown and so it need not be explained more fully. .The voltage of the source of direct voltage 1 'is chosen to be-of such magnitude that the indica-tor shows a maximum width of the light spot if the voltage between the terminals l is equal Vto zero .'that is to say when the Areceiver is tuned correctly. The voltage applied to the control grid 25 of the indicator tube t, which Voltage lvdetermines the width of the light spot, is de- `pendent'on the'voltage drop across potentiometer and hence will vary in magnitude, following anode voltage variations of tube 2.

' `The .operation o1" :the circuit-arrangement is as follows: .lf 'the upper one of the two terminals `I (thatis to say the terminal connected to the 'control-.grid 2l of thezpentode 2) becomes negative withfrespect to the other terminal, the anode current of the tube 2 drops and the anode voltage rises. The `control-grids 25 of the triodes associated with .the indicator system become less negative'and'the size of the light spot (and if there is aplurality, of the light spots) decreases. y INow, if'the said terminal becomes positive rela- .tivelyfto the other terminal, it can be ensured by suitable adjustment-of the tube 2 that the anode .ccurrentifdecreases again, with the Yresult that volts.

the anode voltage increases and the light spot of the cathode-ray indicator decreases in size. This operation is based on a distribution of the current between the anode 24 and the screengrid 22. In the first case referred to the anode current drops jointly with the screen-grid current and in the second case the anode current decreases while the screen-grid current increases.

The decrease of the anode current in the second case can be explained as follows. Owing to the constantly decreasing anode voltage at an increasing anode current there will be a moment when the anode voltage becomes lower than the screen-grid voltage; approximately from this point the anode current no longer increases, so that as the cathode current increases the screengrid current alone increases. Now the suppressor grid becomes more and more negative, because the voltage across the resistance is constantly increasing. Owing to this the anode current-decreases further, whereas the screen-grid current increases to a greater extent. The effect of the suppressor grid may, if necessary, be inuenced by giving this grid a negative bias; this bias may be supplied, for example, by a battery 9.

It follows from the above that at a given voltage between the terminals I theanode current of the tube and the width of the light spot of the indicator have extreme values. Thus, the circuit is adjusted in such manner that this extreme value occurs when the receiver is tuned to the frequency of the incoming oscillations. As a rule, the voltage received from the frequency detector has the value zero, so that the circuit must be adjusted in such manner that the extreme value of the anode current occurs when the voltage supplied to the terminals I has the value zero. In this case the circuit-arrangement acts as a zero-voltage indicator. The correct adjustment of the circuit is ensured by regulating the electrode voltages and by suitable proportioning of the resistances 3, 4, 5 and 6. When the voltage applied to the terminals I has the value zero, the anode and screen grid voltages have substantially equal values.

In a circuit-arrangement as constructed in practice, in which a pentode of the type 6K1 was used, the resistances 3 and 5 had the following values: R3=1Mw and R5=4700w at a negative bias of the suppressor grid of from 0 to 1.5 v. At a negative bias of 12 volts, R5 was 8000er. The main voltage supply conforms to standard practice and may have, for instance, a value of 250 Similarly, potentiometer 4 may have a resistance value of 1Mo, and the tap thereof may be so adjusted that when the voltage applied to terminals I has the value zero, the screen grid potential is approximately 150 volts. 'I'he resistances included in the anode circuits of the triode portions of tube 8 may each have a value of lMw.

Fig. 2 shows a circuit-arrangement which primarily corresponds with that shown in Fig. 1, the anode voltage of the tube 2 serving, however. in a direct manner as the indicator voltage. In this case the indicator comprises a single cathode-ray indicator system without additional triodes. The suppressor grid 23 is given a fixed negative bias by means of a direct voltage source 9. The operation of this circuit entirely corresponds with that of the circuit referred to before and shown in Fig. 1. The variation of the width of the light spot of the indicator, however, ensues in the opposite sense. due to the omission of the triodes. The width of the light spot is determined by the voltage applied to deflection electrode 29, which voltage is directly dependent on the anode voltage of tube 2.

Figs. 3, 4 and 5 show circuit-arrangements in which the voltage received from the frequency detector is supplied directly to two grids of the pentode 2, viz. to the control-grid 2| and to the suppressor grid 23. The indication voltage is obtained from the screen grid 22 and can be taken from the terminal designated I0.

In the circuit shown in Fig. 3, the voltage of the frequency detector is conducted through a duodiode I I to the two grids 2| and 23. The cathode 23 of one of the diodes is connected to the suppressor grid 23, the anode 36 of the other diode to the control-grid 2|. A leak I5 and I6 respectively is connected in parallel to each of the diodes. In the negative phase of the voltage taken kfrom the frequency detector the cathode current,

and hence the screen grid current, decreases With respect to the current set up when the said voltage has the value zero. In the positive phase of the said voltage only the voltage of the suppressor grid assumes a higher positive value, so that the anode current increases and the screen grid current again decreases (the sum of the two currents being constant). The anode and screen grid voltages are adjusted in relation to each other so that when the voltages applied to the control grid 2I and the suppressor grid 23 have the value zero, the screen grid current is a maximum. If the voltage received from the frequency detector has the value zero, which occurs when the receiver is correctly tuned, the screen grid current has a maximum value and the voltage of the screen grid, i. e. the indication voltage, a minimum value.

In the circuit arrangement shown in Fig. 4 the duodiode II is replaced by two resistances I2 and I3. The operation of the circuit is, however, unvaried. For the negative phaseof the voltage taken from the frequency detector it is obvious that the screen-grid current decreases; in the positive phase the voltage of the control-grid shows substantially no increase due to the diode eiect of the control-grid 2I in conjunction with the high series resistance I3, so that even now the screen-grid current decreases. In this case the suppressor grid 23 does not exhibit any appreciable diode effect. Such an effect may, for example, be avoided by causing this grid to emit secondarily to a slight extent. Consequently, the screen-grid voltage, which is used as the indication voltage, exhibits a minimum value in the case of correct tuning.

The same remarks as those made in connection With the circuit-arrangement shown in Fig. 4 apply to that shown in Fig. 5, with the understanding that the suppressor grid 23 and the controlgrid 2I can no longer exhibit a diode eiect in the positive phase by reason of the negative voltage set up across the resistance 5. In this case, the diode effect of the control-grid 2| in the positive phase is taken over by a supplementary diode I4 which is connected between the control-grid 2I and the lower one of the two terminals I.

In the circuit-arrangements shown in Figs. 3 and 5, use is preferably made of a pentode in which the mutual conductances of the suppressor grid 23 and the control-grid 2I are of about the same order of magnitude. In the circuit-arrangement shown in Fig. 4 there is preferably employed a similar pentode which, in addition, exhibits a very low grid current at positive grid voltages.

einem-841? htl'y an additional Supplementary volta'ge w "ose "valuef dpen'dsf on the sig'r'ialiv` c c M gnal,"4 the'saiditubes"havef'passing through' them; an." importanti-*anode current duev to W ch' tlieL Voltage-"at thedee'ctng plates de` creass-:f` Irf'; oir-tireA contrai-y; a signal is received, the;V regulting'voltage for'f the" automatic gain' contro 'decreases'itlie ahodej current ofthey two tubes, tiratore deeeting---piatesare,influenced byfthemaiau"voltageonly; Doet@ this, in tu' srice'cffsignais,unefindieatorfsystem regist'r aV e'sul diierentfromtliat'in' thecase of correo,tuningtoasignaif I cuit' siiowir in F1 automatic saiirco'ntrol. `W "wefclai'rn 1 2 l dioator"circuitifarrangement for'v iid'catiri-g 'variations in frequency `about a' given frequency value, comprising frequency responsivev means for producing a'rst dire'ct'voltage having" amplitude"A and sign f variations about a given am'- p'lit'ude value: proportional" tovari'ations of said fequency'about'thesaid given frequency value, ajdischarge tube liaving inl the order named a catnod'ei-'asc'reengridan'd'an anode, and meansY to: vary the distribution of" current between` said screen grid and said anode, said means compris# in'g ai iirst: controltgrid interposed between said cat odeL and saidscreen grid, a second" control 'grid interposedbetween said screengrid and said an'odc' ineens-tofapplysaidffirstdirect voltage at valuestliereofbelowsaidY givenvalue to oneof said'cont'rol grids, andrneansV toapply' a directv voltage 'proportional` to 'said rst direct voltage at values' thereof' above said` given value' t0- the othero'f said "control grids. c c

tuning indicator circuit arrangement for" indicating variations in" frequency aboutV a givenA frequency' value, comprising frequency responsive means' for producinga rstj direct voltage having/'amplitude landi-sign variations about a, given amplitude value "proportional to'Variations of said frequency aboutthe` said given frequency value', a discharge tube "having in therorder named a' cathode; 'a screen grdand an anode; means to' Vary the distribution of. currentbetween said screen grid andsaid anode; comprising a' control g'rid: interposed between' said cathode and said screen grid, asupprefss'or grid interposed between said: screen grid and said anode,'me`ans to apply said rst"direetvoltage.to` said control grid and a first impedance element coupled between said cathode andis'a'id suppressor grid to' apply t'osaidv gf 1 by?replacing:y the`.source ofi 75r given amplitude 'value"proportionaLtov variationsV suppressor fgi I tionalg saidif first direct `rvoltage, ,a second vimpedance"elementicoupled between? said.v anodefand;

said!l catlfio'cle,` am output indicator, means Vto 1derive a-controlvoltageffromsaidvsecond impedance elementf-andfmeansf tof/apply: said control voltage to said output indicator.'

3iv A tuningrindicator circuitV varrangement vfor indicating va'ri'ations inf frequencyl about! a .given frequency val-ue; comprising' frequency responsive* means# for. producing a: rst ,direct voltager having?arnplitl'lde-fl and.v signvariationsabout a givenfaamplitudefvalue fproportional l to variations of' said frequency abou-tfth'e. said given`l .frequency value, a dischargev tube having in tlfe'ior-'dernamed Vary-thee distribution of currentb'etvveen said` screen` grid Vand said anode comprising a control grid interposed 'betweenA said I cathode and said screen'gridasuppressor grid interposed between saidfsereengrid and-'said anode, means to'applyl sai'df-rst di-rect voltagegto said control grid, a first impedance element coupledf between :said cathode andisaid'suppressorT grid to .apply-i to saidsup-V presso'rV grida second direct voltage proportional tov said i'rs't directv vol-tagef andmeans' to apply substantiallyequal directp'ctentials to lsaid anodel aridi saidfis'ereenlgridf at' input?levelsn ofv said ii'rs't' directvoltage substantially equalV to said' given amplitude value,y asecond 'impedance element coupled bet-'Ween'esaid lanodeY and said' cathode, an.outputtuning-indicator, means wto derive a controll Voltagefrom saidsecondirnpedance;

element; andf means to "applyf'said control voltage 1 tofsaidoutput tuning indicator.-

'4iy A tuning indicatorcircuit'arrangement for indicating-:variations f in"y frequency about a given frequencyK value, comprising" frequency respon sivev means? for producingV aI first .direct Voltage havingamplitude and sign-variations about a given' amplitude 'value l proportional to variations of said Ifrequencyfaboutthe" saidl given frequency value, adi'Sc-liarge'tubehaving in the order named a catho'defalvscreen gridand an anode, meansfto` r, vary the idistribi-ltion of current between said screen grid and said; anode comprising a control gridinterposed between said cathodel and said screen g-rid, asuppressor grid interposed between said"'screen grid and said? anode, means to apply saidr'st direct Vvoltagev tofsaid control-grid, a first impedance element coupled 'between' said cathode and said suppressor grid to apply to said suppressor grid avsecond direct voltage proportional toI Said-"firstu direct voltagev and means to apply substantially equal directpetentialslto said anode an'd'said screen grid at input levels of said first direct voltage Substantially equal to said given'v amplitude value, ya secondi4 'impedance element coupled between 'said anode and said cathode, an output' vindicating' device comprising two parallelv dischargef'patlisfeach havingfa cathode, a control grid andan' anode', acathode ray indicating system having a pair ofVv deflecting plates` and means to couple each of thefanodes of said discharge paths to a respective defiecting plate, means to" derive-a control voltageV from said second impedancen element, and means to apply said controlcvoltage to the grids of said' discharge paths. c

5. A tuning indicator circuit arrangement for indicating' variations inv frequency about a given frequency va1ue, comprising frequency responn sivemeans for producing a rst direct voltage liavingj amplitude and sign variations about`- a "-.allvs'e'co'nd (direct voltage:-Y propor-i of said frequency about the said given frequency value, a discharge tube having in the order named a cathode, a screen grid and an anode, means to vary the distribution of current between said screen grid and said anode, comprising a control grid interposed between said cathode and said screen grid, a suppressor grid interposed between said screen grid and said anode, means to apply said first direct voltage to said control grid and an impedance element coupled between said cathode and said suppressor grid to apply to said suppressor grid a second direct voltage proportional to said first direct voltage, an output indicator having a control electrode, and means to couple said anode to said control electrode.

6. A tuning indicator circuit arrangement for indicating variations in frequency about a given frequency value, comprising frequency responsive means for producing a first direct voltage having amplitude and sign variations about a given amplitude value proportional to variations of said frequency about the said given frequency value, a discharge tube having in the order named a cathode, a screen grid and an anode, means to vary the distribution of current between said screen grid and said anode comprising a control grid interposed between said cathode and said screen grid, a suppressor grid interposed between said screen grid and said anode, means to apply said first direct voltage to said control grid, a first impedance element coupled between said cathode and said suppressor grid to apply to said suppressor grid a second direct voltage proportional to said first direct voltage and means to apply substantially equal direct potentials to said anode and said screen grid at input levels of said first direct voltage substantially equal to said given amplitude value, an output tuning indicator having a control electrode, and means to couple said anode to said control electrode.

7. A tuning indicator circuit arrangement for indicating variations in frequency about a given frequency value, comprising frequency responsive means for producing a first direct voltage having amplitude and sign variations about a given amplitude value proportional to variations of said frequency about the said given frequency value, a discharge tube having in the order named a cathode, a screen grid and an anode, means to vary the distribution of current between said screen grid and said anode, said means comprising a first control grid interposed between said cathode and said screen grid, a second control grid interposed between said screen grid and said anode, means to apply said first direct voltage at values thereof below said given value to said first control grid and means to apply said first direct voltage at values thereof above said given value to said second control grid, an impedance element coupled between said anode and said screen grid, and means to derive a control voltage across said impedance element.

8. A tuning indicator circuit arrangement for indicating variations in frequency about a given frequency value, comprising frequency responsive means for producing a direct voltage having amplitude and sign variations about a given amplitude value proportional to variations of said frequency about the said given frequency value, a discharge tube having in the order named a cathode, a screen grid and an anode, means to vary the distribution of current between said screen grid and said anode, said means comprising a first control grid imposed between said cathode and said screen grid, a second control grid interposed between said screen grid and said anode, rst and second unidirectional conductors each having a cathode and an anode, means to couple the cathode of said first conductor to the anode of said second conductor to dene a junction, means to couple the anode of said first conductor to said first control grid, means to couple the cathode of said second conductor to said second control grid and means to apply said first voltage to said junction to apply to said first control grid a second direct voltage at values of said first voltage below said given value, said second voltage being proportional to said first voltage, and to apply to said second control grid a third direct voltage at values of said first voltage above said given value, said third voltage being proportional to said first voltage, an impedance element coupled between the screen grid and anode of said tube, and means to derive a control voltage across said impedance element.

9. A tuning indicator circuit arrangement for indicating variations in frequency about a given frequency value, comprising frequency responsive means for producing a direct voltage having amplitude and sign variations about a given amplitude value proportional to variations of said frequency about the said given frequency value, a discharge tube having in the order named a cathode, a screen grid and an anode, means to vary the distribution 'of current between said screen grid and said anode, said means comprising a rst control grid interposed between said cathode and said screen grid, a second control grid interposed between said screen grid and said anode, first and second resistors each having two terminals, means to couple together one terminal of each of said resistors to form a junction, means to couple the other terminals of said resistors respectively to said first and second control grids and means to apply said first direct voltage to said junction to apply to said first control grid a second direct voltage at values of said first voltage below said given value and to apply to said second control grid a third direct voltage at values of said first voltage above said given value, an impedance element coupled between said anode and said screen grid, and means to derive a control voltage across said impedance element.

10. A tuning indicator circuit arrangement for indicating variations in frequency about a given frequency value, comprising frequency responsive means for producing a direct voltage having amplitude and sign variations about a given amplitude value proportional to variations of said frequency about the said given frequency value, a discharge tube having in the order named a cathode, a screen grid and an anode, means to vary the distribution of current between said screen grid and said anode, said means comprising a first control grid interposed between Said cathode and said screen grid, a second control grid interposed between said screen grid and said anode, first and second resistors each having two terminals, means to couple together one terminal of each of said resistors to form a junction,- means to couple the other ends of said resistors respectively to said first and second control grids, a unidirectional conductor having an anode and a cathode, means to couple the anode of said conductor to said first control grid, means to couple the cathode of said conductor to ground potential, a first impedance element coupled between the cathode of said tube and ground potential and means to apply said first direct voltage to said junction to apply to said first con- REFERENCES CITED The following references are of record in the file of this patent:

Number 10 f UNITED STATES PATENTS Name Date Anderson Mar. 26, 1940 Bruck Sept. 10, 1940 Levy May 6, 1941 Baumgartner Oct. 21, 1941 Herold et a1 June 16, 1942 Maynard Feb. 15, 1944 Trevor July 3, 1945 

